Jan. 19, 2006 | On a recent winter afternoon in San Francisco's well-heeled Marina district, there's blood on the sidewalk.

Spilling out of the garage of a neat yellow house, dozens of cardboard boxes overflow with a smorgasbord of frozen raw meat and bones sealed in plastic bags. There's pork and beef from Niman Ranch, and whole quail from Cavendish Game Birds of Vermont. It looks like an upscale butcher has been pillaged by a modern-day Robin Hood, who left the spoils for the taking: lamb, chicken, goat, turkey, rabbit, buffalo -- a veritable Noah's Ark of high-quality protein plunder.

Straining at his leash, a golden retriever is overcome by lust, sniffing frantically at the inside of a box, drinking in the lingering scent of flesh and blood. Not to worry; this dog surely will get more than a nose-full later because the thousands of pounds of meaty carnage piled up here is all for dogs and cats.

It's monthly delivery day for San Francisco Raw Feeders, a buyers group with some 350 human members who strive to feed their animals a diet rich with raw meat -- and not just any meat, but sustainable, antibiotic- and steroid-free meat and bones from cows, pigs and poultry raised and slaughtered on small farms.

Joyce Chin is here to get chow for her eight greyhounds. She looks at the haul and stifles a laugh. "If my mother only knew the stuff that I feed my dogs, she would be horrified because a lot of this would go to feed people in China," she says. "People in America don't even eat a lot of these cuts."

That's true of the pork neck bones and feet, as well as the green tripe with trachea and gullet. Here's 5 pounds of beef hearts for $13.20, 12 pounds of beef livers for $25.80, and a 10-pound case of lamb breast bones for $20.

Tina Maria van der Horst, a tall blonde wearing a blue fleece jacket and jeans, is loading up her trunk with Niman Ranch pork neck bones and beef ribs. She's driven three hours in traffic from Grass Valley, Calif., to make the monthly pickup for her three Rhodesian Ridgebacks. She's been feeding them a raw diet for almost four years.

"I was a kibble person before that, and never again," says van der Horst. "All the little problems they had were instantly solved with the raw diet -- tooth problems, inflammatory bowel disease, ears that accumulated wax. They even smell better. It's like a car that's running well." Van der Horst spends $180 a month to feed her dogs (a 50-pound bag of kibble costs $21). But she thinks the price comes out in the wash. "You're sure to save in the end because you're not going to be running to the vet all the time with allergies, ear infections and teeth cleaning," she says.

Yes, the organic, sustainable, locally grown food craze has migrated off the dinner plate and into the dog dish and cat bowl. In recent years, dozens of raw feeding groups and co-ops have sprung up around the country. Pet owners from Texas to Kansas to Pennsylvania and Washington are trading treasured recipes as well as tips on the best source for whole rabbit.

Pet food companies aren't standing by and watching the customers most willing to spend money on their pets negotiate directly with farmers and ranchers. People annually spend $13 billion on dog and cat food, and pet companies are chomping at the bit to cater to organic customers. So far the Purinas haven't entered the fray but start-ups like Primal Pet Foods offer pre-mixed grinds of raw pet diets for sale at Whole Foods Market and boutique pet stores. Primal sells 65,000 pounds of frozen meals per month in 15 states including Illinois, South Carolina and Wisconsin. Jeffrey's Natural Pet Foods, with two locations in San Francisco, pulls in $300 a day in raw food sales at one of its neighborhood stores.

Although many San Francisco raw feeders say they are vegetarians, they see no contradiction in buying gore by the case for their animals. They view their dogs and cats as domesticated carnivores that should be powered by raw protein, not by packaged, processed, preservative-laden kibble made out of who knows what.

Just over a week ago, their suspicions about commercial pet food got some grisly confirmation when 100 dogs in the United States died from contaminated pet food sold under the Diamond, Country Value and Professional brands, now under recall. The food was contaminated with a toxin that wastes the liver, causing vomiting, orange-colored urine and jaundice. The toxin occurs naturally in corn crops that experience wet conditions following a drought. Diamond states that last summer it was rejecting one or two shipments per week of corn because of high levels of the toxin, but some slipped by. Meanwhile, the Pet Food Institute, which represents pet food manufacturers, issued a statement to reassure the public that most pet food is safe.

Raw feeders are not reassured. They insist their pet diets are safer than supermarket brands of pet food, and that dogs and cats get more vitamins and nutrients out of a raw piece of flesh than processed kibble or canned food, largely because "raw" is more natural.

The veterinary establishment is not sold. Neither the American Veterinary Association nor the British Veterinary Association endorses the health benefits of raw food. Both organizations caution that animals fed raw meat run the risk of contracting food-borne illnesses. The British veterinary group declares that "there is no scientific evidence base to support the feeding of raw meat and bones," and warns humans they risk exposing themselves to bacteria like salmonella.

The raw feeders find the dire warnings laughable.

Joanie Levin-Yarlick, a dog trainer, arrives at San Francisco Raw Feeders with her 12-year-old border collie, Levi. "He eats better than I do," she says. The dog sticks out his tongue, happily panting. "You eat better than I do," she coos.

Levin-Yarlick, who wears a white baseball cap and white sweat shirt with the words "Catholic Dogs Gone Bad" emblazoned over a cartoon of three fornicating pooches, says that Levi's diet includes chicken backs, necks and feet, turkey necks and beef bones. She's here not just for the meat, but also to sell T-shirts and sweat shirts, like the one she's wearing, to benefit a local animal nonprofit. One T-shirt displays two doggies kissing and says: "Don't Ask. Don't Tell."

The freezer back home at Levin-Yarlick's place is stuffed with raw food for Levi. "It's his freezer," she says. "I have nothing in it but ice cubes." But Levi's choice repast is not limited to flesh. It also includes a veggie mash that his doting owner makes out of broccoli, carrots, sweet potatoes, red chard, parsley, garlic, ginger, kelp, alfalfa, zucchini or squash, but never bananas or avocado.

Levin-Yarlick attests that switching her border collie from kibble to this homemade meat- and vegetable-rich diet has given him a lustrous coat and cleared up his bad skin. Since she started making her dog's meals, he's had more energy, better teeth, and even, she says, "his poop is nicer -- it's harder and smaller." But as passionate as Levin-Yarlick is about Levi's transformation on his homemade fare, she doesn't talk about Levi's diet with her vet. "She doesn't agree with the raw diet, so we don't discuss it."

Levin-Yarlick contends that raw food is a natural way to feed dogs. "When they evolved in the wild, nobody cooked their food for them," she says. "They killed their prey and they ate it."

Her view is supported by one of the gurus of raw feeding, Dr. Richard Pitcairn, a University of California at Davis-trained vet who is the author of "Dr. Pitcairn's Complete Guide to Natural Health for Dogs and Cats," which has sold more than 400,000 copies since it was first published more than 20 years ago. "A lot of this is common sense," Pitcairn says. "How have animals eaten for hundreds of thousands of years? Why should we think that the processed foods that we're feeding them are any better?"

At the heart of raw feeding is the conviction that the rise of the pet food industry over the last 60 years has weaned dogs and cats from the foods most natural to them. Instead, it's hooked them on a bunch of low-quality processed junk food that has a long shelf life, making it cheap and convenient for humans but not good for animals.

Raw feeders see the big pet food companies as offshoots of the human food industry, providing a market for all the waste not deemed fit for people. Say a chicken in the slaughterhouse has a cancerous growth on its wing. That goes into pet food, while the rest of the chicken is slated for human consumption, Pitcairn attests. The pet food trade association dismisses the allegation. Other goodies in pet food? Animals that died on the way to the slaughterhouse and even road kill, Pitcairn claims.

Turning that mishmash into kibble, he says, produces food that is overloaded with too many carbohydrates that dogs and cats, especially cats, don't need. In fact, some vets have experimented with treating feline diabetes by putting diabetic cats on a high-protein, low-carb diet, known, of course, as the "Catkins" diet.

Advocates of raw feeding say most vets receive minimal training in nutrition and simply go along with the nutritional guidelines of pet food companies, even peddling their diets in their offices. Many of the chronic health problems common in today's dogs and cats -- the kind of problems that constitute vets' bread-and-butter -- clear up with a more natural diet, according to Dr. Pitcairn.

"Sixty years ago, there was no such thing as commercial kibble," says Kasie Maxwell, founder of the San Francisco Raw Feeders, who spends about $300 a month feeding her two 7-year-old Great Danes and recently rescued 15-year-old Labrador retriever. Before she started this meat market for pets, Maxwell, a vegan, used to shop for her dogs at Whole Foods. She'd pick up chicken, turkey, beef and lamb -- "whatever they had that looked good, organic, hormone-free and antibiotic-free" -- to the tune of $500 a month.

Most of the raw feeders are casually dressed in jeans, and some, in suits, obviously cut work early to make the pickup. Maxwell, 34, is thin and pale, with red streaks in her dark hair. She wears a black knit cap, black pants and a red plaid jacket. She used to be a veterinarian tech, horse trainer, and information technology manager, but now works at home making her own line of doggie herbal treatments and remedies.

Maxwell read Dr. Pitcairn's book in the early '90s and tried the recipes in them with a 9-year-old kitty named Gem that was suffering from multiple health problems. Maxwell attests that the diet didn't just make Gem feel better, it changed her personality: "Upon switching her to raw, she became like a completely different cat," Maxwell says. "I caught her as a feral cat, and she was a little bit feisty and skittish. But she became really outgoing, really pleasant to be around, really sweet." The cat also lost weight, her arthritis went away, her teeth and overall health improved. Gem lived to be 22.